Identification of two highly sialylated human tear-fluid DMBT1 isoforms: The major high-molecular-mass glycoproteins in human tears

Benjamin L. Schulz, David Oxley, Nicolle H. Packer, Niclas G. Karlsson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)


Human open eye tear fluid was separated by low-percentage SDS/PAGE to detect high-molecular-mass protein components. Two bands were found with apparent molecular masses of 330 and 270 kDa respectively. By peptide-mass fingerprinting after tryptic digestion, the proteins were found to be isoforms of the DMBT1 gene product, with over 30% of the predicted protein covered by the tryptic peptides. By using gradient SDS/agarose/polyacrylamide composite gel electrophoresis and staining for glycosylation, it was shown that the two isoforms were the major high-molecular-mass glycoproteins of > 200 kDa in human tear fluid. Western blotting showed that the proteins expressed sialyl-Lea. After the release of oligosaccharides by reductive β-elimination from protein blotted on to PVDF membrane, it was revealed by liquid chromatography-MS that the O-linked oligosaccharides were comprised mainly of highly sialylated oligosaccharides with up to 16 monosaccharide units. A majority of the oligosaccharides could be described by the formula dHex0→2NeuAc1→xHexxHexNAc x(-ol), x = 1-6, where Hex stands for hexose, dHex for deoxyhexose, HexNAc for N-acetylhexosamine and NeuAc for N-acetylneuraminate. The number of sialic acids in the formula is less than 5. Interpretation of collision-induced fragmentation tandem MS confirmed the presence of sialic acid and suggested the presence of previously undescribed structures carrying the sialyl-Lea epitopes. Small amounts of neutral and sulphated species were also present. This is the first time that O-linked oligosaccharides have been detected and described from protein variant of the DMBT1 gene.

Original languageEnglish
Pages (from-to)511-520
Number of pages10
JournalBiochemical Journal
Issue number2
Publication statusPublished - 1 Sep 2002
Externally publishedYes


  • Eye
  • Glycosylation
  • Mucin
  • O-linked oligosaccharide
  • Sialyl-Le
  • Tear film


Dive into the research topics of 'Identification of two highly sialylated human tear-fluid DMBT1 isoforms: The major high-molecular-mass glycoproteins in human tears'. Together they form a unique fingerprint.

Cite this